package gitea

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"

	"git.unkin.net/unkin/forgebot/internal/provider"
)

type webhookPayload struct {
	Action     string `json:"action"`
	Comment    *commentPayload `json:"comment,omitempty"`
	Issue      *issuePayload   `json:"issue,omitempty"`
	Repository *repoPayload    `json:"repository"`
	PullRequest *prPayload     `json:"pull_request,omitempty"`
}

type commentPayload struct {
	ID   int64  `json:"id"`
	Body string `json:"body"`
	User struct {
		Login string `json:"login"`
	} `json:"user"`
}

type issuePayload struct {
	Number      int  `json:"number"`
	PullRequest *struct{} `json:"pull_request,omitempty"`
}

type prPayload struct {
	Number int `json:"number"`
	Head   struct {
		Ref string `json:"ref"`
	} `json:"head"`
}

type repoPayload struct {
	FullName     string `json:"full_name"`
	DefaultBranch string `json:"default_branch"`
}

func (c *Client) ParseWebhook(body []byte, secret string) (*provider.WebhookEvent, error) {
	var payload webhookPayload
	if err := json.Unmarshal(body, &payload); err != nil {
		return nil, fmt.Errorf("unmarshal webhook: %w", err)
	}

	if payload.Action != "created" || payload.Comment == nil {
		return nil, nil
	}

	event := &provider.WebhookEvent{
		Action:     payload.Action,
		Repository: payload.Repository.FullName,
		CommentID:  payload.Comment.ID,
		Body:       payload.Comment.Body,
		Author:     payload.Comment.User.Login,
	}

	if payload.Issue != nil {
		if payload.Issue.PullRequest != nil {
			event.Type = "pull_request_comment"
			event.PRNum = payload.Issue.Number
			if payload.PullRequest != nil {
				event.Ref = payload.PullRequest.Head.Ref
			}
		} else {
			event.Type = "issue_comment"
			event.IssueNum = payload.Issue.Number
		}
		event.Ref = payload.Repository.DefaultBranch
	}

	return event, nil
}

func VerifySignature(body []byte, secret, signature string) bool {
	if secret == "" {
		return true
	}
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(body)
	expected := hex.EncodeToString(mac.Sum(nil))
	return hmac.Equal([]byte(expected), []byte(signature))
}